Papers by Charles Carrigan
The Magma Energy Program of the Geothermal Technology Division is scheduled to begin drilling a d... more The Magma Energy Program of the Geothermal Technology Division is scheduled to begin drilling a deep (6 km) exploration well in long Valley Caldera, California in 1989. The drilling site is near the center of the caldera which is associated with numerous shallow (5-7 km) geophysical anomalies. This deep well will present an unparalleled opportunity to test and validate geophysical techniques for locating magma as well as a test of the theory that magma is still present at drillable depths within the central portion of the caldera. If, indeed, drilling indicates magma, the geothermal community will then be afforded the unique possibility of examining the coupling between magmatic and hydrothermal regimes in a major volcanic system. Goals of planned seismic experiments that involve the well include the investigation of local crystal structure down to depths of 10 km as well as the determination of mechanisms for local seismicity and deformation. Borehole electrical and electromagnetic...
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AGU Fall Meeting Abstracts, Dec 1, 2012
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Pure and Applied Geophysics
Isotopic ratios of radioxenons sampled in the atmosphere or subsurface can be used to verify the ... more Isotopic ratios of radioxenons sampled in the atmosphere or subsurface can be used to verify the occurrence of an underground nuclear explosion (UNE). Differences in the half-lives of radioactive xenon precursors and their decay-chain networks produce different time-dependent concentration profiles of xenon isotopes allowing isotopic ratios to be used for tracking UNE histories including estimating the time of detonation. In this study, we explore the potential effects of post-detonation cavity processes: precipitation of iodine precursors, gas seepage, and prompt venting on radioxenon isotopic evolution which influences UNE histories. Simplified analytical models and closed-form solutions yielding a potentially idealized radioactive decay/ingrowth chain in a closed and well-mixed system typically have limited application by not including the partitioning of the radionuclide inventory between a gas phase and rock melt created by the detonation and by ignoring gas transport from the ...
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This study employs a coupled thermal–hydrologic– mechanical (THM) model to investigate flow chann... more This study employs a coupled thermal–hydrologic– mechanical (THM) model to investigate flow channeling associated with reservoir thermal drawdown. Flow channeling refers to the phenomenon that the fractures carrying more flow tend to cool faster and may subsequently dilate more than fractures carrying less flow, thereby causing increasingly severe flow concentration into the a small number of fractures. Our study discovers that the anisotropic thermal stress in a cooling reservoir tends to loosen fractures that are normal to the primary flow direction more than do fractures along the primary flow direction. This mechanism can counteract the flow channeling potential by promoting a diffuser flow pattern. We also found that the significance of the effects of this mechanism dependent on certain inherent characteristics of the fracture network. Fracture network patterns that are prone to and those with strong inherent resistance to flow channeling need to be identified.
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Journal of Geophysical Research: Solid Earth
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The Non-proliferation Experiment (NPE) is contributing to the development of gas sampling methods... more The Non-proliferation Experiment (NPE) is contributing to the development of gas sampling methods and models that may be incorporated into future on-site inspection (OSI) activities. Surface gas sampling and analysis, motivated by nuclear test containment studies, have already demonstrated the tendency for the gaseous products of an underground nuclear test to flow hundreds of meters to the surface over periods ranging from days to months. Even in the presence of a uniform sinusoidal pressure variation, there will be a net flow of cavity gas toward the surface. To test this barometric pumping effect at Rainier Mesa, gas bottles containing sulfur hexaflouride and {sup 3}He were added to the pre-detonation cavity for the 1 kt chemical explosives test. Pre-detonation measurements of the background levels of both gases were obtained at selected sites on top of the mesa. The background levels of both tracers were found to be at or below mass spectrographic/gas chromatographic sensitivity thresholds in the parts-per-trillion range. Post-detonation, gas chromatographic analyses of samples taken during barometric pressure lows from the sampling sites on the mesa indicate the presence of significant levels (300--600 ppt) of sulfur hexaflouride. However, mass spectrographic analyses of gas samples taken to date do not showmore » the presence of {sup 3}He. To explain these observations, several possibilities are being explored through additional sampling/analysis and numerical modeling. For the NPE, the detonation point was approximately 400 m beneath the surface of Rainier Mesa and the event did not produce significant fracturing or subsidence on the surface of the mesa. Thus, the NPE may ultimately represent an extreme, but useful example for the application and tuning of cavity gas detection techniques.« less
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... Jun 1999. Research Org, Lawrence Livermore National Lab., Livermore, CA; Defense Nuclear Faci... more ... Jun 1999. Research Org, Lawrence Livermore National Lab., Livermore, CA; Defense Nuclear Facilities Safety Board, Washington, DC (US). Sponsoring Org, USDOE Office of Environmental Management (EM) (US). Subject, 54 ...
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Papers by Charles Carrigan